martin



July 31, 1923.

T. G. MARTIN PARTY LINE TELEPHONE SYSTEM inal Filed March 1, 1910 2 Sheets-Sheet 1 WVEA/TOR: 7 & 0% m VV/T/VESSES d-MM ' July 31, 1923.

T. G. MARTI N PARTY LINE TELEPHONE SYSTEM -2 Sheets-Sheet 2 inal Filed March 1, 1910 IlllllllllllHl v W/TNESSES Patented July 31, 1923.

3 UNITED STATES TALBOT o. MARTIN, or CHICAGO, ILLINOIS, ASSIGNQR TO AUTOMATIC nL-ncrnro COMPANY, or CHICAGO, ILLINOIS, A conroRA'rION or ILLINOIs.

PATENT-OFFICE.

1 PARTY-LINE TELEPHONE SYSTEM.

Application am: March 1,1910, Serial No. 546,582. Renewed September 20, 1916. Seri'a1 No. 121,515.

cation.

invention relates to telephone exchange systems in general, but more particularly to party-line telephone systems, and

especially to systems in which automatic switches are employed and controlled over the two sides of the-telephone line in series,

there being no operating grounds at the substations thereof.

An object of my invention is to provide means for selectively signaling the subscribers ona party-line in an automatic or semi automatic telephone exchange system of that kind in which the automatic switches are controlled over the two sides of the calling line in series, systems of this kind being ordinarily known as two-wire systems, as distinguished from systems in which operating grounds are employed at the substations, which latter are commonly known as threewire systems.

Another object is to provide a two-wire system having one or more connectors for seizing the called lines in accordance with the last digit of any called number, which are capable of doing this in any case, notwithstanding that the called line is also the calling line, which is, of course, the case when one party-line subscriber calls another on the same line, and which are provided with means for selectively signaling the called party-line subscriber.

Another object s to provide an arrange ment whereby when a party-line subscriber is called whose telephone has been taken out or discontinued. the call will be received by a manual switchboard operator, andwherebyother subscribers on the said line may be called in the regular way withouthaving the call received by the said operator, thus making it possibleto direct all calls for subscribers whose telephones have been taken out to a manual switchboard, even "though one or more of the telephones thus taken out or discontinued were on party-lines, the arrangement being such that the operator is never called except when the call is for a alike.

subscriber whose telephone has beenftaken out or dlscontmued.

It is also an object to provide certain details'and features of improvement tending to increase the general efiicienc-y and serviceability of a telephone exchange system of this particular character.

To the foregoing and other useful ends my lnvention consists in matters hereinafter set forth and claimed.

In the accompanying drawings Figures 1 and 2 represent diagrammatically a complete circuit connection between a calling substation A (Fig. l) and 21. called substatlon A (F ig. 2), in a system embodying the principles of my invention.

Fig. 1 represents diagrammatically a party-line equipped with number of telephones A, A and A The party-line is connected to an individual or line switch C at the central ofiice. A group of line switches C is controlled by a common mechanism D which is usually called a master switch. At E is shown a first selector switch andat F a so-called second selector is represented.

In Fig. 2 there is represented a second party-line. only one of the substations (A) of which is shown. At 0 is shown a devicewhich may be'connec-ted to a party-line to signal an operator or exchange attendant switch C (Fig. 1). At H is shown my improved connector for completing connection with party-lines. At L, L, L and L are show-Ila number of ringer generators and at M a busy signaling machine is represented. A battery B having one terminalgrounded is provided for the purpose of supplying current for operating the central oflice switches and for talking purposes; y

3 is a detail view ofa portion of the connector switch The'substations may be of any suitable or approved type. Those with which I have elected to illustratemy invention are all Substation A, for example, comprises a receiver-2, switch-hook'ii, transmitter 4, induction coil 5, ringer 6, condenser 7. impulse wheel 8,'impulse springs 9 and 10 arid a ringing push button '11. The switch-hook 3 controls the substation cir-. cuits through the medium of the cam arm l2. When the receiver is on the hook the arm 12 maintains the spring 14in contact with the spring 13, thereby bridging the ringer 6 and condenser 7 across the line con- The impulse wheel 8 is provided with a number of impulse teeth 18 and is secured to a shaft 19 to which there is also secured a dial (not shown) provided with finger holes. When the impulse wheel is rotated forward by the dial the impulse springs are not operated, but as the impulse wheel returns to normal position the impulsespring 9 is forced out of engagement with the spring 10 a number of times, depending i upon the digit called, by the teeth 18. The

5 ing of a number of such groups of springs push button 11, when depressed, serves to remove the short-circuit from the resistance 20. The ringers of the different substations are of the well-known harmonic typethat is, they are adapted to be actuated by ringing current of a certain frequency and not by other frequencies. The ringer of each telephone on a line may be adapted to be rung by a different frequency.

The line switch C is of the general type disclosed in British Patent No. 26,301 of 1906, and in the Western Electrician of Chicago, Illinois, of January 25, 1908, but

is modified slightly to operate in a socalled two-wire system, i. e, a system in which no ground connection is required at the substation for operating the central offioe apparatus. As here represented the line.

switch C comprises a plunger (not shown) attached to a plunger arm 21 which is adapted to be attracted by the magnet 22. The circuit of the magnet 22 is controlled by the calling subscriber through the me dium of the relay 23. A cut-off relay 2 1 is provided by means of which the switch 0 may be disconnected from the line. The springs of the relay 21 may also be operated by the plunger arm 21. WVhen the plunger arm 21 is attracted by the magnet 22 the plunger forces the springs 25, 27, 29 and 31 into engagement with the springs 26, 28, 30 and 32, respectively. 'Although only one set of springs 25,26, 27, etc, is shown, each line switch is provided with a bank consist- 7 each set forming the terminals of a trunk line leading to a selector switch E. *Each trunk line is multiplied through the corre sponding bank springs of a number of switches C.

The master switch D is a modified form of the master switch shown in the said British patent and the Western Electrician,

mally rest in looking engagement.

The master switch comprises essentially a motor magnet 33 for operating the ratchet wheel 34:, a bank of contacts'comprising a common segment 35 and'a number of individual segments a, and relays 36 and 37. The ratchet wheel 34: is connected with a so-called plunger shaft, with which latter the plungers of the idleline switches C nor- A continued rotary motion of the said wheel gives to the plunger shaft an oscillatory motion to move the idle plungers back and forth in front of the bank of trunk terminals. Secured to the plunger shaft there is a cam 88 having on its surface a number of openings adapted to be engaged by the pin 39 on the armature 40. The openings in the cam 38 are so spaced that the pin 39 may engage one of said openings only when the plungers that are engaged with the plunger shaft are in a position directly in front of a trunk terminal. I

The selector switch E is of the general type disclosed in United States Letters Patent No. 815,321, granted March 13, 1906, to Keith, Erickson and Erickson, being modiiied somewhat to operate in a two-wire system. Briefly, the selector comprises a set of wipers 41, 12 and 43 carried upon a shaft having a vertical motion controlled by the vertical magnet 44 and a rotary motion controlled by the rotary magnet 45. switch comprising the wipers 46, 17, 48 and 49 is well known and is controlled by the private magnet 50 in the usual manner. The operation of the selector is controlled by the calling subscriber through the medium of the double-wound line relay 51. The relays 52, 53 and 5 1 deenergize slowly after their energizing circuits have been broken. The slow action may be obtained in several ways, but preferably by securing a heavy copper ring around one end f the core. Means for releasing the selector are provided in the release magnet 55 which is disconnected from the battery by the separation of the off normal springs 56 and 57 as longas the switch shaft is in its normal position. In this instance the mechanism is released immediately upon the energization of the release magnet rather than by its deenergization, as shown in the said selector patent. The selector F is similar to the selector E with the addition of one side switch wiper.

The connector H is of the general type disclosed in-United States. Letters Patent No. 815,176, granted March 13, 1906, .to Keith, Erickson and Erickson, being modified, however, to operate in a two-wire system and having means for selecting different current generators. The general features of the connector are very similar to those of the selectors. The connector is provided with a back-bridge relay 58 through which the The side- "indicated in thedetail View, Fig. 3.

line isprovided with talking current, and a ringer 59 for connecting the generator with the called line. In the connector the doublewound line relay of the selector is replaced by tw single-wound relays 60 and 61. The means whereby difierent generators may be selected comprises a pair of wipers 62 and 63 attached to a ratchet wheel 64: which is adapted to be rotated by means of the magnet 65. This mechanism may be conveniently mounted upon a plate attached to the upperpart of the. frame of the switch, as The wipers 62 and 63 are adapted to engage a number of pairs of contacts, each of which pairs is connected to a ringer generator L, L, L or L These generators each produce ringing current of a different frequency. For example, the generator L produces the proper frequency for actuating the ringer at substation A, the substation A is signaled by the generator L, while the ringer at substation A will respond only to current from the generator L The wipers 62 and 63 are connected to the springs of the ringer relay 59, so that the frequency of the ringing current which will be projected over the line upon the energization of the said ringer relay depends upon the position of the wipers 62 and 63. Although only four sets of contacts for the wipers 62 and 63 are shown, it is evident that any suitable number may be used. The ratchet wheel 64: is'held in its operated position against the tension of a spring (not shown) by the pawl 66. When the release magnet 67 is energized to release the connector it also withdraws the pawl 66, as shown in Fig. 3, to permit the wipers 62 and 63 to be restored to normal position. Secured to the periphery of the wheel 64 is a small bushing which normally holds the spring 68 out of engagement with the spring 67. As soon as the wheel 64 is rotated one or more steps the bushing 68* permits the spring 68 to en gage the spring 67. 1

The apparatus shown at 0 consists of a relay 69 and a harmonic polarized relay 70 which is similar to the usual harmonic ringer except that no gongs are. provided. By a harmonic relay is meant a relay that will respond to a current of a certain frequency, but which will not respond to other frequencies appreciably higher or lower. The armature of the relay 7 O controlsa pair of springs71 and 72 which control the circuit of the relay 69. Fromthe relay 69 a trunk line leads to an operators key K. This trunk line be made common to a number of relays 69. t

In order to give a clearer'understanding of my invention I will give a complete description of the various operations that take place when one subscriber calls another. It will first be assumed that the subscriber A (Fig. l) desires to communicate with the substation A the number of which will be assumed to be 22201. Since the impulses for the last digit of a number are employed in the connector switch to operate the fre-. quency selector, the first four digits reprw sent the number of the line and the last digit represents the number of the substationvon the line. It is thus'evident that the numbers of all substations on any particular line will differ only in'the last digit.

The removal of the receiver at the substation A preparatory to making a' call closes a bridge across the line conductors l6 and 17 through the transmitter 4:, one Winding of the coil 5 and impulse springs 9 and 10, as previously explained. The closure of this bridge across the line completes a circuit through the line relay 23 of the line switch C. This circuit extends from ground G through the springs 73 and 74, line 17, thence through substation A and back over the line 16, through the springs 7 5 and 76, relay 23, contact point 77 and armature 40 to the battery lead 78, thence through ba tery B to ground G. The relay 23, upon energizing, operates to close a circuit extending from ground G through the springs 7 9 and 80 and magnet 22 to the battery lead 7 8, thence through battery B to ground G. T he magnet 22, upon energizing, operates to thrust the plunger of the line switch into the bank and to separate the springs 75 and 74 from the springs 76 and 78, respectively. This operation of the springs 74 and 75 breaks the circuit of the relay 23, allowing it to deenergize to disconnect the ground Gr from the magnet 22. The magnet 22 does not deenergize when the ground G is disconnected, because at the same time a holdsubstation A and back over the line 16,

through springs 25 and 2 6, relay 83, side switch wiper l6 and winding 82 of the relay 51 to the battery lead 78; The relay 51, upon energizing, operates to close a circuit extending from ground .G through the i springs Stand 85 and relay 52 to the battery lead 78. The relay 52 energizes upon disclosure of this circuit, operating to shift the spring'88 out of engagementrwith the spring 87 and intoen'gagement. with the spring '89, and'to close contact between the springs 90 and 91. The engagement of springs 90 and 91 completes a circuit extending from ground G through springs 91 and 90 01 the relay 52, springs 92 and 93 of the relay 94, bank springs 28 and 27, cut-ofi" relay 24 and magnet 22 to the battery lead 7 8. The current flowing over this circuit serves to maintain the magnet 22 energized after the relay 23 has deenergized, as previously stated. The engagement of the springs 90 and 91 of the relay 52 also extends a ground potential from ground G to and through the bank springs 28 and 27, as before traced, and thence over conductor 95 to the private bank contact 96 of the connector H (Fig. 2) thence to the corresponding contact in the bank of each connector which has access to the line of the calling substation. This ground potential prevents any other line from obtaining a connection with the calling line over the conductors 191 and 192 while it is busy.

The engagement of the bank springs 29 and 30 of the line switch C closesa circuit extending from ground G through said springs, master switch bank contact point 97 which corresponds to the trunk seized by the switch C, wiper 98, segment 35 and relay 36 to the battery lead 78. The relay 36, upon energizing, operates to close a circuit through the relay 37, which in turn attracts its armature 4:0, which armature unlocks the plunger shaft by withdrawing the pin 39 from the cam 38, and closes a circuit through the motor magnet 33 and interrupter springs 99.

Since the motor magnet circuit includes the interrupter springs 99, the said magnet operates in a manner similar to that of a buzzeras long as the armature 40 engages the contact point 100. The continued operation of the magnet 33 serves to rotate the ratchet wheel 34 step by step to move the plungers that are locked with the plunger shaft away from the trunk occupied by the switch C toward the next one. After the plunger. shaft has been moved a short dis tance the wiper 98 leaves the contact 97, allowing the relays 36 and 37 to be deenergized. The armature of the relay 37 cannot fall back immediately upon the deenergization of the relay, because the opening in the cam 38 which was engaged by the pin 39 has been moved out of register therewith. The motor magnet 33 will-continue to operate to advance the idle plungers until the next opening in the cam 38 passes under thepin 39, whereupon the armature 410 falls back, locking the shaft against further rotation and breaking the operating circuit of the magnet 33. If the next trunk after the one just seized had been busy the wiper 98 would have found a ground potential upon the next contact after the contact 97, and consequently the relays 36 and 37 would have remained energized while the next opening was passing under the pin 39 and the idle plungers would have been carried past the busy trunk to an idle one. It is evident that being moved from'one trunk to another.

The foregoing is the condition of the cen tral ofiice apparatus immediately after the receiver is removed fromthe switchdiook at the calling substation. The operation of t 1e substation calling device for the first digit 2 twice momentarily forces the spring 9 out of engagement with the spring 10, each time breaking the circuit of the line relay 51 of the selector E. The trunk relay 83 which, it will be remembered, was included in the circuit of the selector line relay 51 is operated by the impulses, but has no utility except when the calling and called substations are on the same line, as will be explained later. Each time the line relay 51 of the selector deenergizes in response to the impulses from the substation it permits the spring 84: to disengage the spring 85 and to engage the spring 86. Since the relay 5). is slow acting it does not have time to deenergize during the momentary interruption of its circuit at the springs 84: and 85; consequently the engagement of the springs 84 and 86 closes a circuit through the vertical magnettd. This circuit extends from ground G through the springs 84: and 86, 88 and 89, private magnet relay 54:, vertical magnet 44: and side switch wiper 48 to the battery lead 78. The vertical magnet receives two impulses over this circuit, operating to raise the switch shaft and wipers 41, 4:2 and 13 two steps to a position opposite the second row or level of bank contacts. The private magnet relay 5- 1, which is included in the energizing circuit of the vertical magnet, is energized by the first impulse; but being a slow-acting relay, does not have time to deenergize during the momentary interruption of its circuit between impulses. In its operated position the relay 5 1 closes a circuit extending from ground G through the springs 101 and 101 and private magnet 50 to the battery lead 78. Shortly after the lastiinpulse is delivered to the vertical magnet the relay 54- deenergizes, breaking the circuit of the private magnet 50, which in turn deenergizes, permitting the sideswitch to pass from first to second position. The passage of the side switch wiper 4.8 from first to second position disconnects the battery from the vertical magnet 44: and closes a circuit through the rotary magnet 45. This circuit extends from ground G through the interrupter springs 102, rotary magnet 15, relay 53 and side switch wiper48 to the battery lead 78. The rotary magnet 45, upon energizing, attracts its armature, which operates to rotate the wipers one step, presses down the armature of the'private magnet 50 and opens the circuit of its own magnet. at the interrupter springs 102. The armature of the rotary magnet thereupon falls back and, if the trunk line upon the terminalsv of which the wipers have just been rotated is idle. the armature of the private magnet falls hack also, permitting the side switch to pass to third position. Ifthe first trunk. of the second level is busy, however, the private wiper 4'3 finds the first private hank Contact rounded in a manner to be explained later. he engagement of the wiper 13 with a grounded contact completes a circuit extending" through the side switch wiper 19, contact point 103 and private magnet 50 to the battery lead 78. Theprivate magnet is energized bycurrent flowing over this circuit and prevents the. side switch roin passing to third position when the rotary armature falls back. With the side switch thus locked in second position the rotary magnet will continue toadvance the wipers step hystep until the privatewi-per 43" engages a nongrounded contact of an idle trunk, whereupon the private magnet50 deenergizes and permits the side switch to pass into third position. The movement of the side switch wiper 48 from second position breal-ts' th'e circuit of. the rotary magnet- 45, and the wipers 46 and 47 extend the. line connection through the shaft wipers 41 -and 42'to the second. selector Fl V Upon the completionof' the connection to the second selector the line relay 10 4: and release relay 105 are energized in the same manner in which; the corres'pondingrelays of the selector E were, first energized. The relay 105, upon energizing,' provides a guarding ground potential at the first. selector private bank contacts of the seized trunk. and closes a holding circuit through the relay 52 of the selector E. This circuit f extends fromv ground G through the side switch wiper 1.06 andsprings 108. and 107 to the private bank contact 109 and to the corresponding contact inthe bank of each selector which has accessto the trunk leading to theselector From the bank con-- tact 109 the, circuit extends through the Wiper 13,; side switch wiper i9' (in, third p'osition), springs I10'and111. and releaseretarymagnet 15 and remains energized for an l-IlStEl-Ilt. after the wipers have heenriotated the last step.

The selector F responds to the operation.

of the substation calling device for the second digit 2, operating in. the same manner as explained for the first selector E to extend the connection to an idle trunk line loading to a connector switch Upon com 1 pletion of the connection with. the connector H the relays 60 and 61. are: both energized,

closing a' circuit extending from ground Gr through the springs 112 and 113 of there I 118, upon energizing, provides. a guarding potential for the-seized trunk and. provides a holding circuit for the. release relays of the selector switches. This circuit extends from ground. 9 through the sides'witch. wiper 119', springs 120 and. 121, conductor 122',-

private bank contact and wiper I25,*side switch 126', springs 12'? and 128 to the conductor 128 from which latter one branch passes through the relay 105, while another hranch passes through'the sideswitch wiper 106 to the. relay 5 2 of the selector E over a circuit which has been previously traced. r i Y The connector H is now in position to re} ceive impulses for the remaining digits of the desired number, When the calling device is operated for the, third digit 2 the bridge across the calling line is againopened twice, allowing the, relay 60 to twice mo; mentarily be restored to; normal. position. Each time the relay 60 deenergizes itclose's a circuit through the vertical. magnet 130'. This circuit. extends. from ground G through. the springs 1'14 andl131, 132 and 139,

private ma-gnet relay 133,. vertical magnet 130. and side switch wiper 134' to the brttery lead 78. The vertical magnet receives two impulses over the circuit just traced, operating toraisethe wipers two steps; The private magnet relay 133 is energized by the first impulse and remains in its operated po sition until all the impulses are delivered to the vertical magnet. In its operated? posi tien, besidesclosing the circui't'of the pri vate magnet 135., the. relay 183short circuits the relay 6-1 by the engagement ofthe springs 1.86 and 137. relay 61 is for the purpose of decreasing the resistance of the. circuit of the relay 60 while it is. operating" The d'eenergizationjjoi" the private mag-net relay 133 after all the impulses have been delivered to the vertical This" short-circnitingof the magnethreaks the circuit of the private magnet 135, which then operates "tocause the sideswi'tch'to pass from first to second position. The passage oihthe side switch wiper 134 from first to second position shifts the battery connection from the vertical magnet 130 to the rotary magnet 138. Each time the line relay 6O deenergizes in response to the impulses tor the fourth digit 6 a circuit is closed through the rotary magnet 138. Thiscircuit extends from ground G through the springs 114 and 131, 132 and 139, private magnet relay 133, springs 140 and 141 of the relay 142,.rotary magnet 138 and side switch wiper 134 to the battery lead'78. The private magnet relay 133 operates, in the manner already explained, to close the circuit of the private magnet 135 as long as the impulses are being delivered to the rotary magnet. After the last impulse is delivered the relay 133 deenergizes and'opens the circuit of the private magnet 135. If the called line is idle the private magnet thereupon deenergizes to'permit the side switch to pass to third position. It the called line is busy, however, the side switch remains in second position and the calling substation is given the busy signal in the following manner: Whenever a line is busy there is a guarding ground potential estab' lished at the connector private bank contacts of that line. Consequently, when the private wiper 143 is rotated onto the contacts of a busy line the ground potential is extended from the guarded private bank contact through the side switch wiper 147 and springs 148 and 149 and winding of the re lay 142 to the spring 146 of the private magnet relay 135. When the relay 133 deenergizes, the spring 145 engagesthe spring 146 before it disengages the spring 137. Thus the private magnet remains energized by the ground extending from the private bank contact of the busy line through the relay 142, and at the same time the said relay 142 also becomes energized over the same circuit. The relay 142, uponenergizing shifts the spring 149 into engagement with the spring 150, whereby the holding ground of the relay 142 and private magnet 135 is transferred from the private bank contact to ground G the circuit extending from the side switch wiper 119 and springs 120 and 121. Since the private magnet was not deenergized after the impulses were delivered to the rotary magnet, the. side switch did not leavesecond position and the calling substation is given the busy signal over a circuit extending from the battery ,lead 78 through the secondary winding of the induction-coil of the busy signaling machine M, through the private magnet springs 151 and 152, ringer relay springs 154 and 155, condenser 156, thence over the heavy conductors shown in Fig. 1 to and through the substation A and back through the relay of the connector H to the starting point. The calling substation will continue to receive the busy signal until the receiver is restored to the switch hook, when the central oflice apparatus will be released in a manner to be explained. It is evident that when the connector H is thus locked on a busy line the springs 140 and 141 of the relay 142 are separated, thus preventing the operation of the rotary magnet 138 when the last digit is called. 4

The foregoing is an explanation of how the busy signal is received in case the called line is busy; but in the drawings it is assumed that the line was idle when called. When the private magnet relay 133 deenergizes after the wipers have been rotated onto an idle line, the circuit of the private magnet is broken. The private magnet thereupon deenergizes', allowing the side switch to pass from second to third position. The side switch wipers 153 and 157 (in third position) extend the line conection through the shaft wipers 158 and 159 to the line of the called substation. The side switch wiper 147 (in third position) provides a guarding ground for the connector private bank contacts of the called line and closes a circuit through the cut-off relay 160 of the line switch C. a This potential and circuit extend from ground G through the side switch wiper 147, shaft private wiper 143 to the bank c ontact 161, and thence to the cor-- responding contact in the bank of each of the connectors which have access to the line #2220. From the bank contact 161 the circuit also extends through the relay 160 and magnet 162 to the battery lead 78. The relay 160, upon energizing, operates to disconnect the line switch C from the line. Although the current flowing through the relay 160 and magnet 162'in series would be strong enough to hold down the armature of the magnet 162 if it were already operated, it is not strong enough to attract it from its normal position. The engagement of the side switch wiper 134 with its thirdposition contact point connects the operating magnet of the frequency selecting mechanism with the battery. lead 7 8, thus placing the magnet 65 in position to be operated for the last digit. 6

The operation of the substation calling device ter the last digit 1 causes the operation of the connector line relay 60 in the same manner as for the two previous digits. Each time the relay 6O deenergizes for this digit it closes a circuit extending from ground G through the springs 114 and 131, 132 and 139, private magnet relay 133, magnet 65 and side switch wiper 134 to the battery lead 78. Each time the magnet 65 is energized the wipers 62 and 63 are rotated one step. Since in this instance the last digit is 1, the wipers are rotated onto the terminals of the generator L, which is assumed to be of the proper frequency to ring the bells at substation A.

As soon as the private magnet relay 133 de- 7 7 gins to be intermittently energized over a circuit extending from ground G through the interrupter 163, springs 164 and 165 of the relay 58, relay 59, springs 166 and 167 of the relay 138., and through the springs 67 and 68.and side switch wiper 134 to the batterylead 78. Although the springs 67 and i 68 engage as soon as the ratchet wheel 64 is noved vone step, the circuit of the ringer relay 5 9 is notcompleted until the relay 133 deenergizes to permitthe springs 166 and 167 to. engage. The private magnet 135 is ener-- gized and deenergized once in the usual manner for the last digit; but since. theside switch has already reached the limit, of its travel, this operation of the private magnet has no effect.

Each time the ringer relay 59 is energized. as above explained, the calling and called lines are disconnected and the generator L is bridged across the called line. The path of the ringing current extends from one terminal ofthe generator L through the wiper 63, ringer relay springs 168 and 154-, side switch Wiper 153, shaft wiper 159, line conductor 169, thence through the ringer 170 Of the substation A and back over the line 171, through the shaft wiper 158, side switch Wiper 157, ringer relay springs'173 and 172, and through the wiper62 to the opposite terminal of the generator L. This ringing current also passes through the, harmonic relay 70 ofthe device 0, but is not of the proper frequency to operate it.

When the receiver at the substation A is removed, or as soon thereafter as the ringer relay 59 is deenergized,'if it happens to be energized at the time, the called substation is provided With talkingbattery current. The circuit of this current extends from ground (al through the side switch wiper 147, lower winding of the back-bridge relay 58, ringer relay springs 155 and 154:, side switch wiper 153,shaft wiper 159, line 169, thence through the impulse springs,-pri'ma-ry winding of the induction-coil and transmitter at the substation A, and back over the line 171thr0ugh the shaft wiper 158, side switch wiper 157, ringer relay spr1ngs173 and 168 and upper winding of therela-y 58 to the battery lead 78. The baclz-brid-ge relay 58, which is included in this circuit, is energized and, by separating the springs 16 1and 165, prevents further energization of the. ringer relay after the called subscriber has answered. An uninterrupted conversation may now be carried on between the two connected substations over the heavy conductors shown in the drawings.

After the-conversation is completed the release of the central, oilice switches; is init ated by the restoration of the receiver to the switch-hook atthe calling; substation.

The separation of the springs 15. and 14: by the restoration of the-receiver at the substation A destroys the circuits of the relays; 60 and 6.1 of the connector H. These re; lays, upon deenergiz-ing, break the, holding circuits of the release relays 118, 1Q5 and 52 of the switches H, F and E, respectively. The release relays, upon deenergiz-ing, operate to. close the; circuits of their respective release magnets. The circuit of the release magnet 67 of the connector H extends from ground G through the springs 114: and 131 of the relay 60, springs 132 and 174- of the relay 118, magnet 67 and oft normal springs 175 and 176 to the battery lead 78. The magnet 67, upon energizing, not only allows the side switch and shaft to. be restored to normal position, but withdraws the pawl 66 from the wheel 64 to allow the wipers 62, and 63 to be released. The selectors F and E are released in the; same manner as the connector H. The deene-rgi-zation of the. re-

lease relay 52 of the selector E also breaks,

When a substation has been disconnected 7 from a party-line or changed to another line and it is desired that any one calling I for this disconnected number shall be notified of the fact, the deviceshown at. 0' is connected to the line at the central office. i In the present instance it is assumed that the substation #22202 has been disconnected from line #2220 and the device 0 substituted therefor. Any one calling substation :tt22202 will obtain connection with th li #22 0 in, the s me manner as: previously described, after which the frequencyselecting wipers 62 and 63 will be rotated two steps onto; the terminals of the genera,- tor'L. It is understood, of course, that the harmonic; relay 70 at the; device 0 must be adapted to respond to ringing" current of; the same frequency as: wasv required to,

ring the bells at substation #22202, and that the generator L will supply current of such frequency; The relay- 70 responds as soon as current is projected over the line i from the genera-torL and draws its armature down first on one side andthenonthe other.

18? across the line conductors 171 and 169, causing the back-bridge relay 58 of the connector to be energized to cut off the ringing current in the same manner as when the receiver was removed at the substation A The relay 187 is also energized in series with the relay 58, and operates to close a circuit through the lamp 188 which signifies t0 the operator that some one is calling substation #22202. By throwing the key K the operator may connect her talking set with the line to notify the calling subscriber that the substation desired has been disconnected from that line. The relay 39 will be unlocked by the disengagement of the private wiper 1 13 from the contact 161 upon the release of the connector H.

In case the called substation is on the same line as the calling substation the operation of obtaining a connection is the same as described, except that the pushbutton must be pressed to signal the called subscriber. It the subscriber A (#22301) had called substation A (#22302) the operation of the central otlice apparatus would have been the same as when calling substation #22202 except that the connector wipers would have been brought into engagement with the contacts 189, 190 and 96, thus being connected back to the calling line over conductors 191 and 192. As has been previously mentioned, a guarding round is established at the connector bank contact 96 as soon as the line switch C is operated. In order to permit the connector H to complete connection with the calling line this ground potential must be removed or monified for a short time after the connector wipers have been placed incontact with the line terminals. It is the function of the relays 83 and 9 1, which re associated with the trunk leading to the selector E, to so modify this potential at the private bank contact 96 that the connector. may complete connection with the calling line. As previously mentioned, the relay 83 deenergizes each time the substation impulse springs are separated when the calling device is operated. Each time therelay 83 deenergizes, a circu it is closed extending from the ground G at the sele tor E through the springs91 and 90, 193 and 19 1, and through the relay 9% to the battery lead 78. The relay 94, upon energizing, separates springs 92 and 93, thereby removing the short-circuit fromthe resistance 195. The relay 94-is slow acting and consequently remains energized for a short time after the last impulse for any digit is transmitted. It is thus evident that the circuit which tends to lock the private magnet 135 after the digit 0 of the number 22302 is called extends from ground G at the selector E through the springs 91 and 90, resistance 195, bank springs 28and 27, and over conductor 95 to the connector bank contact 96 (Fig. 2), thence through wiper 1 13, side switch wiper 14:7, springs148 and 11-9, relay 142, springs 146 and 145 and through the private magnet 135 to the battery lead '78. Since this circuit contains the resistance 195, suflicient current does not flow to lock the magnet 135, hence the side switch passes to third position in the usual manner. After the side switch has had time to reach third position the relay 94.- deener 'izes, again short-circuiting the resistance 190 and thus again connecting the contact 96 to ground without interposed resistance. It should be stated that although the resistance 195 prevents suthcient current from flowing to lock the private magnet of the connector, it does not reduce the current through the magnet 22 of the line switch C sufficiently to allow it to release its plunger. Also, it is evident that the trunk relay 91 must be slower than the private magnet relay 133 of he connector switch.

it is evident that when connection is cometed back to the calling line by the contor the bridge across that line through calling substation will cause the back ar'dge relay 58 of the connector to be en'- er ized so as to open the circuit of, the ringer relay 5a in the same inanneras when the receiver at the called substation A was removed. In order to ring the substation #22302 the subscriber at substation A must press the button 11. The pressing of the button 11 removes the short-circuit oi": the resistance 20, whichis then included in the bridge across the line conductors 16 and 17. This increase of resistance reduces the current through the back-bridge relay 58 sufficiently to allow its armature to fall back while the line relay 60 still receives enough a current to hold its armature in its operated position. The deenergization ot the relay 58 allows the ringer relay to be intermittently energized, in the same manner as when the substation A was called, until the button 11 is released or the receiver at the called substation is removed. During the time the relay 59 is energized to connect the ringing generator with the line a circuit-is closed extending from ground G through the ringer relay springs 172 and 173, side switch wiper 157,shatt wiper 158, bank contact 189, thence over the conductor 191 to the line switch C and back over the upper heavy conductors, through the switches E and F and through the relay 60 of the connector H to the battery lead '78. The closure of this circuit through the relay 60 is for the purpose of preventing it from chattering to the action of the ringing current.

he switches are released from this connection as in the previous case, but not, however, until the last subscriber has hung up his receiver.

From the foregoing it will be seen that ing apparatus forsaid switch, and means Iprovidc a two-Wire system in which the subscribers on a party line are selectivelysignaled; For thepurposc of this applica- Lion the expression tivo wire system means one in Which'the automatic switches are controlled over the two sides of the calling line inseries, and in "which no operating groundsare employed at the sub-stations. It will" also be seen that I provide a two-'Wire sysparty-line subscriber calls another. on the same line. Again, it willbe seenthat I'provide a party-line system in "which the open ator will be signaled whenever a party-line subscribersliiie is called whose telephone The re has been removed or discontinued. maining subscribers on the party-line will,

h0W"1','l)B called in the regular Way and without signaling the. operator. This canv be done in various ways Without departing from the spirit of my invention. As shown, I provide the operator with a tuned orharmonic signal whichis only responsive to the signaling: current formerly used for the ringer of the subscriber Whose telephone has been taken out or discontinued. In this way the ringing currents used on the same line for signaling the other subscribers will not a'fi'ect the signal at the manual switchboard, and the operator will not be signaled \Vhat I cIaim as my invention is 1. In atelephone-system'a called line, a:

said slo w acting relay for controlling the circuit of-said ringer relay.

2. In a telephone system, a plurality of lines divided into groups, a plurality of sub? stations on said lines, 'an'autoinatic conrrector having motion 1n one plane to select a group" and motion in a plane at right ankles theretoto find a line "in the selected group, a line leading to said connector, means for controlling said connector over two sides of said line circuit in series, afringer relay, a 'slow-act'ing relayand a frequency selectcontrolled by said selecting apparatus and saidHslow-acting relay for controlling the circuit of said ringer relay. 5

3.- In-a telephone system, a calledhncl. a

' plurality of substations onsaid line, an au toma-tic connector switch for finding said line,a line leading to said connector, 21 ringer relay. a slow-acting relay and a frequency selecting apparatus for said switch, and

means controlled by said selectingapparatus and said slow-acting relay for controlling the circuit said ringer relay. V 7

l; In a; telephone system, a plurality of lines divided into groug'ispa plurality of substations on. saidlines, an automatic connector SWitQfl havingmotionin one plane to select a group and JIlOtlOn ma planeat right angles'thereto to find a li "c inthe'a-selected line: leading to said sari ch, ringer relay, a slow-acting relay and 'a' frequency selecting apparatusfor said switch, and

means controlledby said selecting apparatus and said slow-acting relay for'controlling the circuit of saidringer relay.

In a telephone system, a subscribe-rsr .unc, a plurality of substations on said 11110,

l'ecting apparatus, and a release magnet for connector causingthe release of both said and 'l'requency selector.

6. In a te ephone system, a plurality of lines divide-dinto g'roups, a plurality of substations on said lines, an automatic connector having motion in one plane to select a group and motion inua plane at rightangles thereto to find a. linein the. selected group, a line circiiit leading to said switch, means for controlling" said switch over two sides of said line circuit in series, a frequency selecting apparatusimd a release magnet for causing the release of both said-connector and frequency selector. i

7. In a telephone system, a line, a plu rality of substations on said line, means for selectively signaling the subscribcrson-said line, and a manual switchboard provided;

with means for receiving the signal .fwhen the call is fora subscriber Whose telephone has been taken'out or discontinued.

8. In telephone system, a line, a plurality of substations on, said line, means for,

selectively signaling the subscribers on said line, and a-inanua'l switchboard provided.

Witha signal which is responsive only when oneof said selective signaling devices is. operated. Y. t t y 9. In a-tclephone system, a-. line,' a plural ity of substations on said line. means for-se'-.

lective-lvsignaling the subscribers on said line, and an operators signal which is 'res'ponsive only "when a particular one olisaid selective signaling devices is operated-5 .10. In a telephone system, a line, a plus: rality of substations on said-lineymeans for automatically extending a callto' said line,

means :for; signal ing the subscribers on said. line, 'andan operators signal responsive onlyivhen the'call is fora subscriberavhose telephone hasbeen-talzenjiout orv disc0ntinned.v

1.1,. In a telephone system, a line, a Pil erators signal.

- 12. In a telephone system, a line, a'plurality of substations on said line, a connec' tor switch, said switch being provided with a terminal of said line, means for engaging said terminal when one subscriber calls another on the same line, a circuit for providing a guarding potential for said line, a normally short'circuited resistance included in said circuit, and means for removing said short-circuitso as to temporarily reduce the current passing through said guarding circuit so as to permit said connector to connect with the line.

13. In a telephone system. a line, a plurality of substations on said line, a connector switch, said switch being provided with a terminal of said line, means for engaging said terminal when one subscriber calls another on the same line, a circuit for providing a guarding potential for said line. a normally short-circuited resistance included in said circuit. a slow-acting relay for controlling said short-circuit, and means for en ergizing said relay so as to open said shortcircuit to permit said connector to connect with the line.

14;. In a telephone system, a line, a plurality of substations on said line, a connector switch. said switch being provided with a terminal of said line, means for engaging said terminal when one subscriber calls another on the same line. a circuit for providing a guarding potential for said line. a normally shortcircuited resistance included in said circuit. a slow-acting relay for controlling said short-circuit, means for energizing said relay so as to open said shortcircuit to permit said connector to connect with the line, and a second relay included in series in the talking circuit for controlling said slow-acting relay.

15. In a telephone system, a line, a plu rality of substations on said line, a connector switch controllable over two sides of said line in series. said switch being provided with a'terminal of said line. means for engaging said terminal when one subscriber calls another on the same line. a circuit for providing a guarding potential for said line. a normally short-circuited resistance included in said circuit, and means for removing said short-circuit so as to temporarilv reduce the current passing through said guarding circuit so as to permit theconnector to connect with the line.

16. In a telephone system, a'line, a plurality of substations on. said line, a connector switch controllable. over ,two sides of said line in series, said switch being provided with a terminal of said lim -means for engaging said terminal when one subscriber calls another on the same line, a circuit for providing aguarding potential for said line, a normally short-circuited resist ance included in said circuit, a slow-acting relay for controlling said short-circuit, and means for energizing said relay so as to open said short circuitto permit said connector to connect with the line.

' 17. In a telephonesystem, a line, a plurality of substations on said line, a connector switch controllable over two sides of said line in series, said switch being .provided with a terminal of said line, means for engaging said terminal when one subscriber calls another on the same line. a cir-. cuit for providing a guarding potential for said line, a normally shortcircuited resistance included in said-circuit, a slow-acting relay for controlling saidshort-circuit, means for energizing said relay so as to open said short-circuit to permit said connector to connect with the line, and a second relay included in series in the talking circuit for controlling said slow-acting relay.

18. In a telephone system. a line, a plurality of substations on said line. signals for said substations, a manual switchboard provided with a signal. and automatic progressively movable trunking apparatus for selectively signaling either the operator at said switchboard or the subscribers on said line, all of said signals being connected to said line.

19. In a telephone system, a line, a plural ity of substations on said line. an operators signal on said line, means for selectively signaling either the operator or the subscribers over said line.

20. In a. telephone system, a party line, a progressively movable switchfor extending aconnection therefrom, means for placing a guarding potential on said line by operating said switch when one subscriber on said line initiates a call, and means for ringing back on said line withoutremoving said guarding potential.

21. In a telephone system, a pluralit-yof lines, an automatic switch adapted to establish connection with one of said line s, means for extending connection to said switch, an

operators board, and means for automatically switching said connection from said switch to said board after connection is established with said line. v

22. In a telephone system, a two-conductor line, a plurality of stations connected thereto,

means for-signaling a" station on said line, a relay for .controlling'the application of said signaling means, a second relay, said second relay. connected to a conductor of saidline, a trunk line extending to man-- ualswitehboard, a signal for said trunk line, arcalling line,-e battery for operating and talking pur oees, a third relay for connecting a pole 0 said battery over said conductor to energize saild second relay, whereby when the calling line signals for a station on said firstline, theserv'ice of. which has been disa continued, the calling line is connected to the manual switchboard over said trunk N line. i i

In a telephone system, a two-conductor line, a plurality o'fstations connected thereto, means for signaling a station on said line, said signaling means comprising a circuit, a relay for controlling said circuit, a second relay, said second relay connected to a conductor of said line, a trunk line extending to a manual switchboard, a signal for said trunk line, a callingline, a battery for operating and talking purposes. a third relay for con necting a pole of said battery over said conductor to energize said second relay, whereby when the calling line signals for a station on said first line, the service of which has been discontinueth'the calling line is connected to the manual switchboard over said trunk line. l

24. In a; telephone system, a line terminating in the exchange or central ofiice, a plural ity of subscribers stations connected. with said line, a plurality of ringing current gen erators of different character. means for applyingsaid generators to said line to signal the stations thereon, a trunk line extending to a manual switchboard, a signal for said trunk line, a relay connected to said first line when a station thereon is out of service vor disconnected, means whereby calls for the remining stations are received at the respective stations and means including saidrelay whereby calls for the disconnected station are connected via saidtrunk line to-said mannal switchboardand means for operating said signal.

25. In a telephone system, a line terminating in the exchange or central office, a plurality of subscribersstations connected with said line. a plurality of ringing current gencraters of different character, means for applying said generators to said line to signal the stationsthereon, atrunk line extending to a manual switchboard, a signal for said trunk line, a station of said line disconnected therefrom or out of service, means whereby calls for said, disconnected station are connected via said trunk line to said manual switchboard to display said signal, and

means whereby callsfor the remaining stations on said line are received at the respective stations trunk line, a plurality of stations of saidline disconnected therefrom or out of service, means whereby calls for sand disconnected stations are connected via'said trunk line to said manual'switchboard to display said signal, and means whereby calls for the remaining stations on said line are received at the respective stations.

27. In a telephone system, a two-conductor line, a plurality of stations connected to said line, a terminal for said line in the exchange or central office, a ringing current generator for signaling one of said stat-ions,

a calling line, a manual switchboard. a battery for operating purposes, a relay for connecting a pole of said battery to a conductor of said line and means responsive to said battery connection whereby when the calling line signals for a station on said first line, the service of which has been discontinued, the calling line is connected to thh manual switchboard. Y

28. In a telephone system, a two-conductorline, a plurality of stations connected to said line. a terminal for said line in the exchange or central ofiice, a ringing current generator for signaling one of saidsta-t-ions, a calling line, a manual switchboard. a battery for operating purposes. a relay for'connecting a pole of said battery to a conductor of said line and means responsive to said battery connection whereby when the calling line signals for a. station on said first line. the service of which has been discontinued, the calling line is connected to the manual switchboard. a signal at said switch-' board. and means for operating said signal.

29. In a telephone system, a plurality of party lines each having substation signals responsive to signaling currents of different character. sources of signaling current of different character, a calling line. a connector switch accessible to said calling line for extending connections to said lines, means in said connector for selectively associating said sources witha called linein accordance with :1 ca led number, atrunk to an operators position. and means associated with said connector for connecting the calling line with said trunk should the substation corresoondinc to the called number be disconnected.

30. In a telephone system, a party line and a plurality of substations in bridge thereof, caclfsuhstation having a signal responsive to a particular character of ringing current, differ nt sources of ringing current corresponding to said signals, a calling line, a

loo

connector switch for extending said calling line to said party line, means in saidconnector for connecting a particular source of ringing current withsaid party line to signal a wantedsubstation, atrunk extendingto an operators position, and means associated with said connector'for extending the calling same line.

In a telephone system, a party line, a connector switch controllable from the said line to connect with the said lineor other lines. a test terminal for said line accessible to said connector, means for placing a guarding potential on said terminal when the line is calling and means for temporarily lower ing said guarding potential without entirely removing the same in order to'render the said potentialinefiective to prevent said connector from connecting with said lin'e'when one party on the line calls another party on the same line,

In a-telephone systenr'a party line, a connector switch controllable from the said line to connect with. said line or other lines, a test'terrninal forsaid line accessible to said connector, means for connecting said test terminal to one pole of the exchange battery to place a guarding potential thereon when the line is calling. and means for substituting for said potential a potential different from the potential of either pole of the battery in order to permit said connector to connect with said line when one party on the line is calling another party on the same line. I V

34. In a telephone system, a party line, a connector switch controllable from the said line to connect with said line or other lines, a test terminal 'for said line accessible to said connector, means for connecting a guarding ground potential to said terminal when the line is calling, and means for reducing said gound'potential to a value greater than Zero to permit said connector to connect with said line when one party on the line is call ing another party on the same line.

35. In a telephone system, a partyrline, a conn ctor switch controllable from the said line to connect with said line or other lines. a-test terminal forsaid line accessible to said connector, a cut off relay for said line connected to said test terminal, means for placing a guarding potential on said test contact when the line is calling in order to make the linebusy and to energize said out oft-relay, and means for temporarily reducing said guarding potential suiiiciently to permit said line to connect with said line or other lines,i

a test terminal for saidline accessible to said connector, a cut oil relay for said line con-- nected to said test terminal, means for placmg a guarding potential on said test con tact when the line is calling in order to make the lii e busy and to energize said cut off relay, and means for changing said guard ing potential to a value suflicient tomaintain said cutoil relay energized but insutlicientto prevent said connector from connecting with said line when one party on the line calls another party on the same line.

37. In a telephone system, a party line, a partially established reverting connection including a s "itch individual to saidline, a

selector, and a final connector, a grounded re ease trunk conductor extending back to the line switch from said selector for maintaining the line switch in operated position, a. test conductor connectedto said release trunk conductor at said line switch and to a test contact at said connector switch. and means for reducing'the ground. potential on said release trunk conductor suiiiciently to permit said connector to connect with said line when it is operated to complete the said connection but insuiiiciently to permit said line switch to release. i I

In a telephone system, aparty line, a partially established reverting connection'iheluding a switch individal to said line,.a'se lector, and a final connector; a grounded release trunk conductor extending back to the line switch from said selector for maintaining the line switch in operated position, a test conductor connected to said release trunk conductor at said line switch andto a test contact at said connector switch, and means .i or inserting a resistance in the said release trunk conductor toreduce the potential on said test contact sufliciently to permit said connector to connect with said line when it is operated to complete the said connection while maintaining sufiicient current flow to prevent the release of said line switch.

39. In a selective ringingtelephone system. the combination, with a connector switch and means for operating it to connect with a party line, of an auxiliary ringing current selecting switch individual to said connector,- a motor magnet for operating said selecting switch to select the proper ringing current to selectively signal a desired said motor magnet and maintained energized While the same is being operated, ofi' normal contacts closed by said selecting switch at the beginning of its selecting operation, a circuit for said ringing relay prepared by the closure of said off normal con- 10 tacts, and contacts for completing said circuit closed by said slow acting relay when the same deenergizcs at the close of the selecting operation.

Signed by me at Chicago,Co0k County, Illinois, this 18 day of February, 1910.

TALBOT G. MARTIN. iVitnesses:

EDWARD D. FALns, ARTHUR J. RAY. 

